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III. Gm-C Filtering - Epublications - Université de Limoges

III. Gm-C Filtering - Epublications - Université de Limoges

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Technique<br />

Current<br />

Increase<br />

Source<br />

Degeneration<br />

Dynamic Source<br />

Degeneration<br />

Unbalanced<br />

Differential<br />

Pairs<br />

MGTR<br />

Table 8. Comparison of the transconductance linearization techniques<br />

IIP3 and Noise<br />

Performances<br />

3dBm for 3.6mS<br />

Difficult to obtain higher gm<br />

14dBm for 10mS<br />

8.3 10 -18 V 2 /Hz<br />

16dBm for 9mS<br />

13.3 10 -18 V 2 /Hz<br />

21dBm for 2.5mS<br />

9.7 10 -18 V 2 /Hz<br />

7dBm for 10.7mS<br />

9.6 10 -18 V 2 /Hz<br />

21dBm for 10mS<br />

6.5 10 -18 V 2 /Hz<br />

- 103 -<br />

Advantages Drawbacks<br />

Simple technique<br />

Simple technique<br />

High linearity<br />

Linearity versus<br />

noise tra<strong>de</strong>-off<br />

Very high linearity<br />

Power consumption<br />

Noise<br />

Power consumption<br />

Low linearity<br />

Linearity versus<br />

noise tra<strong>de</strong>-off<br />

Linearity versus<br />

noise tra<strong>de</strong>-off<br />

Power consumption<br />

Noise increase<br />

Linearity peak<br />

The MGTR technique shows the best performances. However, the linearity presents a<br />

peak versus the PDA bias that may be very sharp, as it will be discussed later on. Hence, the<br />

sensitivity to this bias will have to be taken into account when linearizing <strong>Gm</strong>-cells by this<br />

means.<br />

In the following, second or<strong>de</strong>r <strong>Gm</strong>-C filters using the best two linearization<br />

techniques, dynamic source <strong>de</strong>generation and MGTR, will be <strong>de</strong>signed and compared.

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